Purification of alkyl aryl hydrocarbons



United States Patent 3,338,983 PURIFICATION OF ALKYL ARYL HYDROCARBONS John A. Thompson, Sarnia, Ontario, Canada, assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Jan. 24, 1964, Ser. No. 339,854 8 Claims. (Cl. 260-674) The present invention relates to the treatment of alkyl aryl hydrocarbons and particularly to the treatment of alkylated benzenes in order to remove color precursors therefrom. Specifically, this invention provides a method for the treatment of alkylated benzenes to remove color precursors therefrom so that they may be sulfonated, particularly with sulfur trioxide and neutralized with alkali to yield detergents which are substantially colorless.

Alkyl aryl sulfonates, principally dodecylbenzene sulfonate, represent the major proportion of the total tonnage of surfactants produced annually in the United States. As produced today, dodecylbenzene sulfonate (which commercially is the sulfonate of a mixture of alkyl benzenes in which the average number of carbon atoms in the alkyl side chains is between 12 and 13) essentially dominates the surfactant field because of its high foaming and detergency properties, good color and odor and low cost.

The detergent alkylate market is, of course, highly competitive at the present time. Detergency performance is of paramount importance in the evaluation of detergent alkylate and usually the competitive products of the same molecular weight distribtuion have equivalent detergency performance. While the color of the sodium sulfonate is of secondary importance to detergency, the present competitive situation has made such color a prime selling factor.

Sulfonation of alkylated benzene and the like is a relatively simple procedure but does present some troublesome problems in commercial operation. The formation of colored by-products or materials which discolor the resultant sulfonates is perhaps the most serious problem. Generally this problem can be minimized by avoiding contact with iron and by using sufficiently pure hydrocarbons. The older and better. known Sulfonation procedure of sulfonating with about 1.3 to 2 parts by weight of 100 to 105 percent sulfuric acid or oleum has more recently given way to the use of free S0 as the agent for sulfonating detergent alkylates since the reaction is practically quantitative thus avoiding the problem of removing excess or spent acid and a detergent of very low salt content is made directly. Unfortunately, however, free 50;, is extremely reactive, hazardous to handle and causes charring unless very careful control is maintained during the sulfonation. Moreover with free S0 as the sulfonating agent the purity of the hydrocarbon materials is extremely important.

It is, therefore, the object of this invention to provide an improved process for treating alkyl aryl hydrocarbons to remove color precursors therefrom.

It is a further object of this invention to provide a simple, effective method for removing color precursors from alkyl aryl hydrocarbons so that substantially colorless sulfonates can be obtained by sulfonating the treated alkyl aryl hydrocarbons and neutralizing the resultant sulfonic acids.

It is also the object of this invention to treat alkyl aryl hydrocarbons to remove color precursors therefrom so that on subsequent sulfonation with free 80;, and neutralization, white or substantially colorless sulfonates are obtained.

These and other objects will appear more clearly from the detailed specification and claims which follow.

It has now been found that color precursors can be effectively removed from detergent alkylates, or alkyl aryl hydrocarbons in which the alkyl groups contain from about 10 to 18 carbon atoms, by treating the alkylates with concentrated sulfuric acid at essentially ambient temperatures with stirring. Thereafter, hydrogen peroxide is added to the acid-alkylate mixture and stirred for a short period while allowing the temperature to rise somewhat. Upon discontinuing the agitation, the acid-hydrogen peroxide mixture separates very rapidly leaving a fairly acidfree alkylate. The acidand hydrogen peroxide-treated alkylate is then subjected to clay treatment in order to remove the residual acidity from the alkylate. The extra cost entailed using hydrogen peroxide in this process is very low in view of the improvement in the quality of the alkylate and the sulfonates produced therefrom. Moreover, any extra cost entailed by the use of hydrogen peroxide is offset by the fact that the volume of alkylate treated per volume of clay used is increased.

The alkylated aromatic hydrocarbons which may be freed of color precursors by the process of this invention are those prepared by the condensation of an aromatic hydrocarbon such as benzene, toluene, ethylbenzene, cumene, xylenes, naphthalene, alpha methyl naphthalene and the like with an olefin of from about 10 to 20 carbon atoms per molecule in the presence of a Friedel-Crafts catalyst. In a preferred embodiment the detergent alkylate is prepared by alkylating benzene with an olefin, preferably a propylene polymer fraction boiling in the range of about 340 to 450 F. which usually contains a major proportion of C polymers with lesser amounts of lower and higher molecular Weight polymers, in the presence of anhydrous AlCl HP or other analogous Friedel-Crafts catalyst.

The acid treatment is effected with sulfuric acid of about to 99% concentration, preferably 98% sulfuric acid, in amounts of from 2.to 20, preferably about 10 liquid volume percent based upon the alkyl aryl hydrocarbon. Contact of the acid and hydrocarbon is effected with stirring at temperatures of from 50 to 200 F., preferably at about 72 F. for from 5 to 30 minutes, preferably about 10 minutes. A small amount of hydrogen peroxide generally less than about 2 wt. percent based upon the alkyl aryl hydrocarbon, as for example by the addition of 1 to 2 liquid volume percent based on the alkylateacid mixture of 30% hydrogen peroxide, is then added to said mixture While continuing stirring for an additional period of about 10 minutes. A rise in temperature to about F. and preferably to not more than 200 F. occurs. Stirring or agitation of the acid-alkylate-peroxide mixture is then stopped and the mixture allowed to separate into a hydrocarbon layer and an acid layer. The hydrocarbon layer separated is substantially acid-free and is then clay treated to remove the residual acidity from the hydrocarbon or alkylate. Clay treatment may be effected by percolating the treated alkylate through a bed of clay or by adding about 0.5 to 2.0 wt. percent of Attapulgus clay based on the alkylate. Instead of Attapulgus, other clays of the montmorillonite or illite type may be used, Sufficient clay is used to treat the alkylate to remove any residual acid therefrom. If clay is stirred into'the alkylate, the clay is separated from the treated alkylate by settling, centrifuging or filtering. The alkylate is then suitable for sulfonation in any desired way, including reaction with 80;, for conversion to the corre- 3 sponding sulfonic acid which on neutralization, for example with caustic soda, yields detergents of excellent color. The following examples are illustrative of the present invention.

Example 1 A detergent alkylate was prepared by alkylating benzene with a polypropylene having an average of 12.0 carbon atoms per molecule using a conventional Friedel- Crafts AlCl -I-ICl catalyst system.

The sample of this detergent alkylate was converted to the corresponding sulfonic acid using fuming sulfuric acid as the sulfonating reagent. Sulfonation was eifected by placing 75 gm. of the above detergent alkylate in a 500 ml. 3-necked flask fitted with a thermometer and a motor driven glass stirrer with a Teflon blade, and connected to a Teflon bellows acid pump. The stirrer is operated at 10001100 r.p.m. and the alkylate is heated to within 5 F. of the desired reaction temperature. With the acid pump already primed, 76.5 gm. of 20% fuming sulfuric acid (1.02 acid/alkylate weight ratio) is added over a period of 20 minutes while continuing stirring and maintaining the reaction mixture at 90 F. The resultant sulfonic acid was neutralized with caustic soda by premixing 11.0 gm. 50% NaOH, 10.0 gm. isopropyl alcohol and 64.6 gm. water and cooling the same in an ice bath whereupon these are added to 14.4 gm. of the sulfonic acids in a cooling (ice) bath maintaining the temperaturer below 120 F. The color of the resultant 10% sodium sulfonate solution is then measured on a Beckman Model B spectrophotometer using a 1 cm. cell. The wavelength selected is 4250 A. and the results reported in percent transmittance. Distilled water is used as a standard of 100% transmittance.

Another portion of the same detergent alkylate was treated to remove color precursors by the addition of 10 liquid volume percent 98% sulfuric acid and stirring at 72 F. for ten minutes. The resultant mixture was allowed to stand for 10 minutes to allow it to separate into two layers. The lower spent acid layer was discarded and the upper alkylate layer was percolated through 30/60 mesh Attapulgus clay to remove residual acidity and give a clear and relatively colorless liquid. One portion of the treated alkylate was converted to sulfonic acid using fuming sulfuric acid as in the conversion of the untreated alkylate and another portion of the treated alkylate was converted to sulfonic acid using free S In this procedure, 1.05 moles of sulfur trioxide (pure grade) is placed in a 300 ml. 3-necked flask equipped with a heating mantle. A nitrogen supply is connected through a rotameter to said 300 ml. flask and thence to a 1000 ml. B-necked flask equipped with a thermometer and a motor driven glass stirrer with a Teflon blade. The flow of nitrogen to the 300 ml. flask is adjusted to 850 liters/hr. The stirrer is started (about 1000' r.p.m.) and one mol of the alkylate is added to the 1000 ml. flask. Temperature in the latter (reaction flask) is maintained at 55 C.:1 C. while the temperature in the 300 ml. flask (S0 vaporizer) is maintained at 40-45 C. during the sulfonation. After all of the S0 has been added, the sulfonation reaction mixture is allowed to age for about 15 minutes. Neutralization of the sulfonic acids was eifected by weighing 10 gm. thereof into a 100 ml. beaker, adding 40 ml. of 2% caustic soda and 10 ml. isopropyl alcohol and adjusting the pH to 89 with 2% caustic. The solution was transferred to a tarred 150 ml. beaker and diluted with suflicient distilled water to obtain a 10% solution for measuring on the Lovibond Tintometer and/ or a solution for measuring on the Beckman Model B spectrophotometer.

Another portion of the same detergent alkylate was treated to remove color precursors by first treating the same with vol. percent of 98% sulfuric acid. The mixture was stirred for 10 minutes at 72 F. To this mixture was then added two liquid volume percent of 30% hydrogen peroxide. The reaction is exothermic causing the temperature to rise to 110 F. The mixture is stirred for 10 minutes during which time the color of the reactants turns from black to a light yellow. The resultant mixture was allowed to settle for 10 minutes. The lower layer is drawn off and discarded, the upper organic layer was then percolated through 2 wt. percent of Attapulgus clay (for small volumes of alkylate a /2 diameter glass column 18" high with 25 cc. of clay was used). The resultant alkylate was substantially colorless and odorless. This treatment of detergent alkylate has been carried out with volumes :from 200 cc. to 5 gallons with essentially the same quality of treated alkylate obtained in each case. Two portions of the resultant treated alkylate were converted to sulfonic acids with fuming sulfuric acid and with free S0 as described above.

The several sulfonic acid products were converted to the sodium salts and aqueous solutions of these salts were tested for color by measuring the percentage of transmittance of ultraviolet light. The results obtained are tabulated in Table I.

TABLE I Percent Percent Transmit- Transmittance l at tance 1 at 4,250 A. 4,000 A.

Sultonating Agent S0 Concentration of Sodium sulfonate. 10 5 Untreated Alkylate 69 conventionally treated Alkylate. 71 48 HgSO /Hg0z Treated Alkylate 72 68 l The percent transmittance measurements were made using a Beckman Model B spectrophotometer. The light source is a tungsten lamp and wavelengths of 4,000 and 4,250 A. were used. The color of the sulfonated alkylate (oleum, 20%) was measured in a 1 cm. cell versus dis tilled water. The sulfonate color of the S0 sulfonated alkylate was measured in a 5 cm. cell versus distilled water: Distilled water being a standard reference of percent transmittance. The higher the transmittance value, the better the color.

2 Fuming Sulfuric Acid.

Example 2 A detergent alkylate was prepared by alkylating benzene with a polypropylene having an average of 13.6 carbon atoms per molecule in a commercial unit using the Friedel-Crafts AlCl -HCl catalyst system as in Example 1.

A portion of this alkylate was converted to the sulfonic sold using S0 as the sulfonating agent and converting the same to the sodium sulfonate described in Example 1.

Four other portions of the detergent alkylate were treated to remove color precursors by the following procedures:

(a) Treatment with chromic acid as described in Example 1 of US. Patent No. 2,932,677.

(b) Treatment with ozone as described in Example 6 of the same US. patent.

(c) The conventional treatment with 98% sulfuric acid as described in Example 1 above.

(d) Treatment with sulfuric acid followed by the addition of hydrogen peroxide as described in Example 1 above.

These treated alkylates were reacted with S0 only TABLE II.-SODIUM SULFONATE COLOR Percent Lovibond (10% Soln.) 'Iransmittanee (5% Soln.) Treating Method Color 1 Yellow 450 Red None 3. 2 22. 17 36 48 Chromic Acid 2. 0 7. 5 42 62 71 zone 1. 9 7. 9 45 64 72 Sulfuric Acid 2. 5 12. 0 30 50 61 H SO4-H30g 1. 5 4. 4 57 73 80 1 High Lovibond values indicate poor colors.

It is to be understood that this invention is not limited to these specific embodiments since numerous variations are possible without departing from the spirit and scope of this invention as defined in the following claims.

What is claimed is:

1. The method of treating detergent alkylates to re move color precursors therefrom which adversely affect the color of alkali metal sulfonates prepared therefrom which comprises treating said deter-gent alkylates with from about 2 to 20 liquid volume percent based on said alkylates of concentrated sulfuric acid at essentially ambient temperatures with agitation for from about 5 to 30 minutes, adding a small amount of hydrogen peroxide to the alkylate-sulfuric acid mixture while continuing the agitation, stopping the agitation to allow the mixture to separate into a hydrocarbon layer and an acid layer, separating substantially acid-free alkylate, contacting the separated alkylate with clay to remove any residual acid therefrom and separating alkylate substantially free of color precursors from the clay.

2. The method of treating detergent alkylates obtained by the condensation of an aromatic hydrocarbon selected from the group consisting of benzene, toluene, ethylbenzene, cumene, xylenes, naphthalene and alpha methyl naphthalene with an olefin of from about 10 to 20 carbon atoms per molecule in the presence of a Friedel-Crafts catalyst to remove color precursors which adversely affect the color of alkali metal sulfonates prepared therefrom which comprises treating said detergent alkylates with from about 2 to 20 liquid volume percent based on said alkylates of concentrated sulfuric acid at essentially ambient temperatures with agitation, for from about 5 to 30 minutes, adding a small amount of hydrogen peroxide to the alkylate-sulfuric acid mixture while contiming the agitation, stopping the agitation to allow the mixture to separate into a hydrocarbon layer and an acid layer, separating substantially acid-free alkylate, contacting the separated alkylate with clay to remove any residual acid therefrom and separating alkylate substantially free of color precursors from the clay.

3. The method of treating detergent alkylates obtained by the condensation of an aromatic hydrocarbon selected from the group consisting of benzene, toluene, ethylbenzene, cumene, xylenes, naphthalene and alpha methyl naphthalene with an olefin of from about 10 to 20 carbon atoms per molecule in the presence of a Friedel-Crafts catalyst to remove color precursors which adversely aifect the color of alkali metal sulfonates prepared therefrom which comprises treating said detergent alkylates with from about 2 to 20 liquid volume percent based on said alkylates of sulfuric acid of about 95 to about 99% conconcentration at temperatures of from about 50 to 200 F. with agitation for from about 5 to 30 minutes, adding up to about 2 wt. percent of hydrogen peroxide based upon the alkylate-acid mixture to the alkylate-sulfuric acid mixture while continuing the agitation, stopping the agitation to allow the mixture to separate into a hydrocarbon layer and an acid layer, separating substantially acidfree alkylate, contacting the separated alkylate with clay to remove any residual acid therefrom and separating allkylate substantially free of color precursors from the c ay.

4. The method of treating detergent alkylates obtained by the condensation of an aromatic hydrocarbon selected from the group consisting of benzene, toluene, ethylbenzene, cumene, xylenes, naphthalene and alpha methyl naphthalene with an olefin of from about 10 to 20 carbon atoms per molecule in the presence of a Friedel- Crafts catalyst to remove color precursors which adversely affect the color of alkali metal sulfonates prepared therefrom which comprises treating said detergent alkylates with from about 2 to 20 liquid volume percent based on said alkylates of sulfuric acid of about to about 99% concentration at temperatures of from about 50 to 200 F. with agitation for from about 5 to 30 minutes, adding a small amount of hydrogen peroxide by adding about 1 to 2 liquid volume percent based on the alkylate mixture of 30% hydrogen peroxide to the alkylate-sulfuric acid mixture while continuing the agitation, stopping the agitation to allow the mixture to separate into a hydrocarbon layer and an acid layer, separating substantially acid-free alkylate, conta-cting the separated alkylate with clay to remove any residual acid therefrom and separating alkylate substantially free of color precursors from the clay.

5. The method as defined in claim 1 wherein the treatment to remove residual acid is effected with 0.5 to 2.0 Wt. percent of Attapulgus clay based upon the alkylate.

6. The method as defined in claim 2 wherein the treatment to remove residual acid is effected with 0.5 to 2.0 wt. percent of Attapulgus clay based upon the alkylate.

7. The method as defined in claim 3 wherein the treatment to remove residual acid is effected with 0.5 to 2.0 wt. percent of Attapulgus clay based upon the alkylate.

8. The method as defined in claim 4 wherein the treatment to remove residual acid is eifected with 0.5 to 2.0 Wt. percent of Attapulgus clay based upon the alkylate.

References Cited UNITED STATES PATENTS 2,932,677 4/1960 Kirk et a1 260674 FOREIGN PATENTS 919,910 2/ 1963 Great Britain.

DELBERT E. GANTZ, Primary Examiner.

C. E. SPRESSER, Examiner. 

1. THE METHOD OF TREATING DETERGENT ALKYLATES TO REMOVE COLOR PRECURSORS THEREFROM WHICH ADVERSELY AFFECT THE COLOR OF ALKALI METAL SULFONATES PREPARED THEREFROM WHICH COMPRISES TREATING SAID DETERGENT ALKYLATES WITH FROM ABOUT 2 TO 20 LIQUID VOLUME PERCENT BASED ON SAID ALKYLATES OF CONCENTRATED SULFURIC ACID AT ESSENTIALLY AMBIENT TEMPERATURES WITH AGITATION FOR FROM ABOUT 5 TO 30 MINUTES, ADDING A SMALL AMOUNT OF HYDROGEN PEROXIDE TO THE ALKYLATE SULFURIC ACID MIXTURE WHILE CONTINUING THE AGITATION, STOPPING THE AGITATION TO ALLOW THE MIXTURE TO SEPARATE INTO A HYDROCARBON LAYER AND AN ACID LAYER, SEPARATING SUBSTANTIALLY ACID-FREE ALKYLATE, CONTACTING THE SEPARATED ALKYLATE WITH CLAY TO REMOVE ANY RESIDUAL ACID THEREFROM AND SEPARATING ALKYLATE SUBSTANTIALLY FREE OF COLOR PRECURSORS FROM THE CLAY. 